CONDITION MONITORING OF RAILWAY TRACK:INSPECTION FREQUENCY AND WEAR LIMIT

Presented By:Rajeev Ranjan2005JIT2527

Introduction Wear and fatigue general track problem.Rail inspection & repair work like grinding

is needed.Frequency of inspection according as

defect rate, axle load and traffic on track.Frequency of inspection and limit on wear

are interrelated.

Outline of Presentation…..

Determination of frequency of inspection.

Limit on wear of track.Limitations of method used.Proposed future work.

Frequency of Rail Inspection

Results produced by FRA, USA was taken as basis.

The mathematical relationships composing the self-adaptive guide for scheduling rail tests have been translated into a nomograph.

Nomograph for scheduling rail tests.

How it works?

Case to illustrate application of nomograph

Results:Simulation of rail testing on a medium density line (60 MGT per year).

Results:Simulation of rail testing on a heavy haul line (120 MGT per year).

RAIL HEAD WEARWear is not a rail defect in the same sense as a

crack, which is a stress raiser and intensifies the local state of stress, but it is a cause of rail removal.

Wear reduces the overall cross-sectional area of the rail, which increases the magnitude of bending and normal stresses in the rail, thereby weakening the load carrying capacity of the rail.

Limit on WearThe methodology to estimate limits for rail head

wear combines the results from two separate sets of calculations.

The first set of calculations estimates limits for rail wear based on fracture toughness assuming a known defect size and a specific loading condition.

Since the defect size is generally not known, a second set of calculations is performed to estimate the critical defect size that should be assumed to calculate limits on rail wear.

A schematic of this first set of calculations.

Assuming that rail wear reaches a limit when the defect grows from barely detectable size (assumed to be 5 %HA) to a critical size in less than one

inspection intervals (assumed to be 20 MGT).

A schematic of the second set of calculations

The results of the two sets of calculations are combined to estimate limits for rail head wear. In other words, the intersection of the two curves; one based on fracture toughness and the other based on the defect growth rate; defines the limits for rail head wear.

Actual and estimated limits for vertical head-height loss.

Actual and estimated limits for gage-face side wear.

Limitations of Proposed Study:1. The fatigue crack-growth data used for test

specimens made from plain carbon rail steel. Such tests should be performed using test specimens made from more modern rail (e.g., rail with head hardening). However rail steel is not an isometric material and there is no existing test methodology for such specimen.

2. The process of head hardening, introduces complexities in the distribution of residual stress and in the microstructure within the rail head. Laboratory tests to determine the fatigue crack growth properties in modern rail steel need to be designed to discriminate among the separate effects of stress intensity factor gradient, residual stress gradient, and micro structural gradient.

Limitations of Proposed Study:3. The engineering analyses to calculate

detail fracture growth neglect the effects of load sequence. However, results from analytical and experimental studies suggest that crack closure cannot entirely explain the differences in crack growth behavior of rail steels due to different load sequences. Thus, the cause of load sequence effects in rail steel remains an open question.

4. The methodology used here can't be used in trend monitoring as past data is required in analysis

Proposed Future Work & Methods:

In developing condemning limits for rail head wear other considerations need to be taken into account in addition to fracture strength for e.g. - vehicle dynamics, lubrication, gauge widening, etc.

There is need of development of standard test procedure for fatigue crack growth using specimen taken from in service rail steel.

There is still no mathematical modeling for the rail steel wear. If a mathematical model gets developed it can easily be related to inspection frequency.

Proposed Future Work & Methods:

The nomograph method can be utilized in determining any plant inspection frequency as a handy approach.

It can even be used in determining oil topping by considering oil losses with time in one chart and contamination level with use in another.

Reference and Bibliography: 1) David Y. Jeong, “Analytical Modelling of Rail Defects and Its

Applications to Rail Defect Management; UIC/WEC JOINT RESEARCH PROJECT ON RAIL DEFECT MANAGEMENT; January 2003.

2) Fausto Pedro García Márquez, Félix Schmid, Javier Conde Collado; “Wear assessment employing remote condition monitoring: a case study”. Wear 255 (2003) 1209–1220

3) Fausto Pedro García Márquez, Félix Schmid, Javier Conde Collado; “A reliability centered approach to remote condition monitoring. A railway points case study” Reliability Engineering and System Safety 80 (2003) 33–40

4) Fausto Pedro Garcia Marquez, Diego Jose Pedregal Tercero, Felix Schmid. “Unobserved Component models applied to the assessment of wear in railway points: A case study” European Journal of Operational Research (2006)

5) Bengtsson Marcus. "Condition Based Maintenance on Rail Vehicles – Possibilities for a more effective maintenance strategy” Bombardier Transportation, Sweden, 2002

6) M. N. Bassim, S. ST. Lawrence and C. D. Liu. “Detection of the onset of fatigue crack growth in rail steels using acoustic emission” Engineering Fracture Mechanics Vol. 41, No. 2, pp. 207-214, 1994

Thank you!

Grinding units with rotating stones